Hello everyone, this article provides a comprehensive summary about the CVE-2025-36041 vulnerability and the IBM MQ service, based on my research and detailed analysis of the service architecture.

1-Introduction to IBM MQ

First, before discussing the vulnerability or anything else, let's understand what IBM MQ actually is:

1-1-Core Features of IBM MQ

• Reliability: Guarantees message delivery even if the system crashes or the connection is lost
• Scalability: Supports large and complex environments such as banks and insurance companies that require processing millions of messages daily
• Security: Supports encryption (SSL/TLS) and authentication to ensure data and communication protection
• Compatibility: Works with multiple operating systems (Windows, Linux, Unix, etc.) and offers diverse APIs like MQI and JMS
• Independence: Uses various protocols to ensure security and service compatibility such as JMS, MQI, MQ over TCP

1-2-Explanation of IBM MQ Protocols:

1-3- JMS — Java Message Service:

JMS is a Java API standard that enables synchronous or asynchronous message sending and receiving across messaging systems. IBM MQ fully supports JMS to integrate Java applications with the messaging system. JMS provides an abstraction layer allowing Java applications to interact with IBM MQ via concepts like Queues and Topics without needing to know the underlying protocol details. It has many advantages such as:

• Easy to use for Java applications.
• Supports different messaging models (Point-to-Point via Queue, or Publish/Subscribe via Topic).
• Simplifies message management in Java environments.

1-4-MQ over TCP/IP :

This is the core protocol used by IBM MQ to transfer messages over the network. IBM MQ uses TCP/IP as a secure and reliable transport method between the Queue Manager and applications. IBM MQ opens specific ports (default port 1414) to communicate over TCP, where data packets containing messages are sent, with guaranteed correct and ordered delivery. It features:

• Reliance on the well-known reliable TCP protocol.
• Can be secured using SSL/TLS to encrypt communications.
• Allows communication between different and diverse systems over the network.
• Supports MQ over SSL/TLS to encrypt and ensure secure message reception.

2-IBM MQ Architecture

2-1-Channels Protocol Stack:

• Base Protocol: IBM MQ channels use a unified transport protocol based on TCP/IP, with application layers dedicated to message handling.
• Message Channel Agent (MCA) Protocol: Manages connections between Queue Managers or between Client and Queue Manager. Includes:
  • Handshake Phase: Negotiation of protocol version, encryption features, packet size, and error management.
  • Data Transfer Phase:Streaming of message data over TCP with message packet fragmentation and reassembly.
  • Flow Control:A window-based flow control mechanism to prevent congestion and ensure QoS.
• Security Layer (TLS/SSL): Uses TLS (usually 1.2 or 1.3) to secure channels, supporting authentication protocols like X.509 certificates.

2-2-Channel Types:

• Sender-Receiver: for QMGR-to-QMGR channels.
• Server-Client: for Client-to-QMGR channels.
• Request-Reply: supports synchronous request/response pattern
• Cluster Sender/Receiver: for cluster channels.

2-3-Message Delivery Mechanisms:

• Persistent vs Non-Persistent Messaging:
  • Persistent:Messages are written to log files before confirming receipt, ensuring no loss even if the system crashes.
  • Non-Persistent:Stored in memory, faster but prone to loss.
• Transactional Integrity:
  • IBM MQ supports Distributed Transaction Processing (DTP) protocols.
  • XA Transactions: Coordinated by an external Transaction Manager.
  • Unit of Work (UOW): Grouping several message operations as a single work unit.
• Message Grouping:
  • Supports grouping messages into meaningful sets with control over delivery order and failure handling.
• Message Priority & Scheduling:
  • Messages can have priorities (0–9), and the Queue Manager uses scheduling tables to ensure higher priority messages are delivered first.
• Storage Subsystem:
  • Log-Based Storage: MQ uses a log system modified for storing persistent messages.
  • Circular logs: rotating files upon reaching a specified size.
  • Checkpointing: ensuring message and data state stability on disk.
• Page Caching:
  • Uses page cache memory to speed up message read/write operations.
  • File System Interaction: MQ depends on local or specialized file systems, supporting advanced file systems like ZFS or GPFS
• Synchronization & Concurrency Control:
  • Locking Mechanisms: Reader-writer locks and mutexes to control concurrent access to queues and messages.
  • Semaphore & Event Signals: Signal arrival of new messages or state changes, increasing resource efficiency.

2-4-Thread Pools & API Layers:

• Thread Pools: Manages pools of threads processing messages in parallel without affecting system performance.
• API Layers & Client Interactions:
  • MQI (Message Queue Interface): Core API layer in C/C++ providing sending, receiving, and message management operations with advanced transactional and messaging capabilities.
  • JMS (Java Messaging Service): Higher-level abstraction based on MQI, offering a standard Java interface for developers.
  • MQSC (MQ Script Command): Command-line tool for managing and configuring Queue Managers, queues, and channels.
  • MQ REST API: Modern RESTful HTTP-based interface enabling control and interaction with IBM MQ via web applications.

2-5- Security Architecture:

• TLS Handshake and Certificate Validation: IBM MQ uses TLS handshake to validate X.509 certificates, with options to restrict cipher suites, encryption keys, and certificate validity.
• Advanced rules control channels, allowing restrictions by IP address, channel name, user, or other properties.
• Access Control Lists (ACLs): Manages fine-grained permissions on resources (Queues, Channels, Topics) at the Queue Manager level.
• Integration with External Security Services: Supports LDAP, Kerberos, RADIUS, enabling centralized and strong authentication.

2-6- High Availability & Scalability:

• Supports clustering of Queue Managers for high availability.
• Load balancing for channels and message queues to optimize throughput.
• Failover mechanisms to ensure continuity of messaging even during outages.

2-7- Queue Manager Clustering:

• Cluster System: A cluster system allows resource replication, load distribution, and automatic message routing among nodes.
• Multi-instance Queue Managers:Ensures multiple active QMGR instances on different servers with automatic failover.

2-8- Load Balancing:

• Via multiple channels and mirrored queues to distribute message traffic and reduce failure points.

2-9- Monitoring & Diagnostics:

• Instrumentation APIs: APIs to capture performance metrics and real-time system status.
• Trace & Dump Facilities:Advanced mechanisms to generate detailed reports on ongoing operations, errors, and message flow.
• Event Notifications:Supports event notifications via MQ Events and integration with SIEM systems or external monitoring.

3-CVE-2025-36041 in IBM MQ:

After knowing the service architecture and everything, let's look at the vulnerability. The CVE-2025-36041 vulnerability is a security flaw in the IBM MQ Channels Authentication mechanism related to SSL/TLS certificate validation when establishing connections between Client and Queue Manager or between Queue Managers.

In IBM MQ environments, communication channels relying on SSL/TLS secure data transport are used. When a channel is set to be authenticated, the Queue Manager must verify the client's certificate before accepting the connection. The vulnerability appears in channels that allow "unauthenticated" connections or when verification conditions are weak.

An attacker can send a forged or invalid SSL certificate, but the Queue Manager wrongly accepts the connection without sufficient verification, allowing bypass of identity verification of the other party (Client or QMGR).

4-Exploitation Stages:

1. Configure a connection channel with the Queue Manager to be either unauthenticated or with lax verification settings.
2. Send a forged or manipulated certificate that appears valid or is accepted inaccurately.
3. Due to a flaw in IBM MQ's verification mechanism, the connection is accepted.
4. After acceptance, the attacker can establish a channel with privileges that might allow reading or sending messages to sensitive queues, or modifying them.

5-Potential Impact

The vulnerability's severity is moderate (CVSS v3.0), meaning it's not critical, but it can be leveraged for:

• Creating unauthenticated channels
• Sending forged messages
• Reading confidential or sensitive messages from queues
• Disrupting the messaging system or injecting malicious data (Integrity Violation)
• Exploitation in other attacks such as eavesdropping, Denial of Service (DoS), or executing malicious code in some scenarios

6- Mitigation Measures

7- Conclusion

While CVE-2025-36041 has a moderate severity rating, it highlights the importance of proper certificate validation in enterprise messaging systems. Organizations using IBM MQ should apply the recommended mitigations promptly and maintain ongoing vigilance through monitoring and regular security assessments of their messaging infrastructure.